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73 lines
4.2 KiB
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<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function ARRAY-ROW-MAJOR-INDEX</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_ar_ran.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_arrays.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_ar_tot.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<HR>
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<A NAME="array-row-major-index"><I>Function</I> <B>ARRAY-ROW-MAJOR-INDEX</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>array-row-major-index</B> <I>array <TT>&rest</TT> subscripts</I> => <I>index</I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>array</I>---an <A REL=DEFINITION HREF="26_glo_a.htm#array"><I>array</I></A>. <P>
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<I>subscripts</I>---a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> of <I>valid array indices</I> for the <I>array</I>. <P>
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<I>index</I>---a <A REL=DEFINITION HREF="26_glo_v.htm#valid_array_row-major_index"><I>valid array row-major index</I></A> for the <I>array</I>. <P>
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<P><B>Description:</B><P>
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<P>
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Computes the position according to the row-major ordering of <I>array</I> for the element that is specified by <I>subscripts</I>, and returns the offset of the element in the computed position from the beginning of <I>array</I>. <P>
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For a one-dimensional <I>array</I>, the result of <A REL=DEFINITION HREF="#array-row-major-index"><B>array-row-major-index</B></A> equals <I>subscript</I>. <P>
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<A REL=DEFINITION HREF="#array-row-major-index"><B>array-row-major-index</B></A> ignores <A REL=DEFINITION HREF="26_glo_f.htm#fill_pointer"><I>fill pointers</I></A>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(setq a (make-array '(4 7) :element-type '(unsigned-byte 8)))
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(array-row-major-index a 1 2) => 9
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(array-row-major-index
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(make-array '(2 3 4)
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:element-type '(unsigned-byte 8)
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:displaced-to a
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:displaced-index-offset 4)
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0 2 1) => 9
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B> None.
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<P>
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<P><B>See Also:</B> None.
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<P>
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<P><B>Notes:</B><P>
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<P>
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A possible definition of <A REL=DEFINITION HREF="#array-row-major-index"><B>array-row-major-index</B></A>, with no error-checking, is <P>
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<PRE>
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(defun array-row-major-index (a &rest subscripts)
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(apply #'+ (maplist #'(lambda (x y)
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(* (car x) (apply #'* (cdr y))))
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subscripts
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(array-dimensions a))))
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</PRE>
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</TT> <P>
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